A plasma processing apparatus, in general, comprises a chamber having therein a susceptor for supporting a body to be processed, and a pair of spaced electrodes. The susceptor can be one of the electrodes. The other electrode can be a showerhead through which various gases are admitted into the chamber to generate a plasma in the chamber. The susceptor electrode and the showerhead electrode are generally made of aluminum. The showerhead electrode is generally connected to a source of RF voltage and the susceptor electrode is generally grounded so that rf power is dissipated between the showerhead electrode and the susceptor electrode to generate a plasma in the gas in the chamber. The particular process achieved in the apparatus depends on the gas or gases used. Some gases result in an etching of the body on the susceptor, and other gases react to deposit a layer on the body.
Prior to performing a processing step in the chamber, it is common to clean the chamber by passing nitrogen fluoride (NF.sub.3) into the chamber. During this cleaning operation, any aluminum parts in the chamber, such as the electrodes, react with the fluorine to form particles of aluminum fluoride (AlF) on the surface thereof. Since aluminum fluoride is an insulating material, the showerhead electrode then has particles of an insulating material over an exposed surface thereof which limit RF power dissipation between the electrodes and thus limit a plasma needed for a particular reaction. The plasma reaction in the chamber can induce micro-arcing which results in the aluminum fluoride flaking off of the showerhead. These particles of aluminum fluoride can deposit on the body being processed and thus adversely affect the characteristics of circuitries and/or devices being formed in and/or on the body.